For example, JP-A-2001-51050 discloses a vehicle radar device comprising a transmission antenna for transmitting a radar wave such as an extremely high frequency wave (millimetric-wave) and a reception antenna having plural antenna elements arranged in the width direction of a vehicle. According to this vehicle radar device, the direction to a forward vehicle (i.e., a vehicle traveling in front of a vehicle having the vehicle radar device) or the like as a reflection object is detected on the basis of the phase difference among reception signals received by the plural reception antenna elements, and also the distance and relative speed between the reflection object and the vehicle having the vehicle radar device (hereinafter referred to as “vehicle concerned”) are detected by subjecting the reception signals thus received to processing such as frequency analysis, etc. The radar device that can detect the direction and distance to the reflection object and the relative speed between the vehicle concerned and the reflection object (the forward vehicle or the like) as described above has been applied to a device for raising an alarm when the distance between the vehicle concerned and each forward vehicle is short, a device for controlling the vehicle speed of the vehicle concerned so as to keep a predetermined distance to the forward vehicle or the like.
In order to enhance the detection sensitivity of the above radar device to a reflection (target) object such as a forward vehicle or the like, it is required that the beam axis of reception beam of the reception antenna should be correctly oriented in both the vertical direction (the vehicle height direction) and the horizontal direction (vehicle width direction) to an area where the reflection object such as the forward vehicle or the like can be detected. The direction (orientation) of the beam axis in the horizontal direction (vehicle width direction) of the reception antenna can be easily identified on the basis of the reception signals of the plural antenna elements arranged in the vehicle width direction, however, the direction (orientation) of the beam axis in the vertical direction (vehicle height direction) of the reception antenna cannot be identified on the basis of the reception signals.
Therefore, it has been generally carried out to equip a radar pointer jig and a level to a transmission/reception unit containing a transmission antenna and a reception antenna, and adjust the mount angle of the transmission/reception unit to the vehicle particularly in the vertical direction by using the radar pointer jig and the level. Accordingly, much labor has been hitherto needed to the adjusting work of the mount angle because it is required to keep high precision to make the beam axes coincident with the laser pointer axes, etc., and also it has been hitherto difficult to keep the precision.